The invention relates to a color television transmission or data storage system having time-division multiplex encoding, the system comprising at least one data generator, at least one data receiver and a transmission or data storage channel arranged between the generator and the receiver, the data generator comprising at least one signal source for producing signals containing luminance, chrominance, synchronizing and identification information, and an encoding circuit for the time-division multiplex encoding of at least a portion of said signals, subjected, where appropriate, to time compression, the encoding circuit having an output for supplying a time-division multiplex encoded signal for transmission via the transmission channel or storage in the data storage channel, the data receiver comprising a decoding circuit coupled to said channel, having a substantially complementary operation to that of said encoding circuit, for supplying signals containing at least luminance and chrominance information which substantially corresponds to the data produced by the signal source in the data generator; and to a data generator and data receiver suitable for use with such a transmission system.
Such a system for, more specifically, transmission is described in a published report "Experimental and Development Report 118/82", published by the U.K. "Independent Broadcasting Authority" (I.B.A.) entitled "MAC: A Television System for High-Quality Satellite Broadcasting". The Report describes several variants of so-called MAC (Multiplexed Analogue Component) picture coding. As can be seen from a Table on page 9 of the Report, it holds for all the variants that in the data generator, which is in the form of a transmitter, the luminance, and the chrominance information are each subjected to time compression, the time compression for the chrominance information being twice that for the luminance information. Of the chrominance information which comprises two components per line period, one of the two is alternately contained, in time-compressed form, in the time-division multiplex encoded signal. In this signal, the luminance information associated with each line period is present in time-compressed form. The Report mentions the factors 2/3 and 3/4 for the time compression of the luminance information and time compression factors equal to 1/3 and 3/8 for the chromiance information. The picture information per line period in the time-division multiplex encoded signal, is sequentially composed from the time-compressed luminance information and one of the two time-compressed chrominance information components associated therewith.
In the receiver, the time-division multiplex encoded signal is derived from the signal received via the transmission channel, more specifically, the satellite connection, and applied to the complementary decoding circuit which, with the aid of the synchronizing and identification information, produces a time decompression (or expansion), as the case may be, of the luminance and the chrominance information and then repeatedly supplies the decompressed chrominance information over the next line period.
In the transmission channel, which in this example, is a satellite connection, there is a limited bandwidth for the transmission of the picture data. Depending on the proposed variation, bandwidths of 8.4 MHz, 7.5 MHz and 6.0 MHz are mentioned in the Report. For the transmission channel bandwidth of 8.4 MHz, a time compression factor of 2/3 is proposed for the luminance information, so that for the non-compressed luminance information, a bandwidth of 5.6 MHz is obtained. For the available picture data channel bandwidths, of 7.5 and 6.0 MHz, a luminance time compression factor of 3/4 is proposed and for the bandwidths of the non-compressed luminance information, the values of 5.6 MHz and 4.5 MHz result. It has been found that for the proposed variants, with the limited transmission channel bandwidth and the proposed structure of the time-division multiplex encoded signal to be transmitted, frequency limitation for the luminance and the chrominance information are required.
In the foregoing, a transmission channel in the form of a satellite connection is mentioned by way of example. The frequency limitations required for data transmission with limited bandwidth also occur with a data storage system having a limited bandwidth. Such a storage system comprises data storage and data reproducing equipment, such as, for example, tape and record recording and reproducing devices.